Planar metal/dielectric waveguides

In this chapter we present an electromagnetic theory of surface plasmons based on theoretical analysis of light propagation in planar metal/dielectric waveguides. The main characteristics of surface plasmons propagating along metal-dielectric and dielectric-metal-dielectric waveguides are introduced and methods for optical excitation of surface plasmons are discussed. 

Another example of a planar waveguide supporting surface plasmons is a thin metal film sandwiched between two semi-infinite dielectric media (Fig. 7). If the metal film is much thicker than the penetration depth of a surface plasmon at each metal-dielectric interface, this waveguide supports two TM modes, which correspond to two surface plasmons at the opposite boundaries of the metal film. When the metal thickness decreases, coupling between the two surface plasmons occurs, giving rise to mixed modes of electromagnetic field. 

Hollow planar waveguides have been fabricated by several techniques, including physical vapor deposition and CVD of silver and dielectric layers on metallic substrates. Nevertheless, better results can be obtained by taking advantage of silicon micromachining techniques. Perhaps the most important advantage of silicon hollow waveguides over other hollow structures is the... 

In Chap. 1 by J. Homola of this volume [1] surface plasmons were introduced as modes of dielectric/metal planar waveguides and their properties were estabhshed. It was demonstrated that the propagation constant of a surface plasmon is sensitive to variations in the refractive index at the surface of a metal film supporting the surface plasmon. In this chapter, it is shown how this phenomenon can be used to create a sensing device. The concept of optical sensors based on surface plasmons, commonly referred as to surface plasmon resonance (SPR) sensors, is described and the main approaches to SPR sensing are presented. In addition, the concept of affinity biosensors is introduced and the main performance characteristics of SPR biosensors are defined. 

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